InN/TiO2 photosensitized electrode

ABSTRACT

The present invention is a photosensitized electrode which absorbs sun light to obtain pairs of separated electron and hole. The photosensitized electrode is fabricated with simple procedure and has low cost. The electrode has excellent chemical resistance and is fitted to be applied in a solar cell device with enhanced sun-light absorbing ability. The present invention can be applied in an optoelectronic device or a hydrogen generator device too.

FIELD OF THE INVENTION

The present invention relates to an photosensitized electrode; moreparticularly, relates to obtaining a photosensitized electrode having anindium nitride (InN) photosensitive layer to be applied in a solar celldevice, an optoelectronic device and a hydrogen generator device.

DESCRIPTION OF THE RELATED ARTS

During recent years, a nano-crystal film technology is utilized in aDye-Sensitized Solar Cell (DSSC) so that the efficiency ofphotoelectrical transformation has gained a great improvement along witha cheap cost. Hence, the cost for a solar cell may quite possibly dropfor about 1/10 to ⅕. The former DSSC basically uses smooth electrode;and its dye molecule layer (such as a ruthenium ligand series, acyanine, a chlorophyll or a dye derived) transforms electric chargeeffectively only at a monolayer close to the semiconductor. Because asmooth electrode has small area for absorption with little absorbingability, its photoelectrical transformation ability is low (less than1%). Recently, a porous nano-structured electrode is introduced forsolving this problem. Because the surface area of the catalyst isthousands times of that of the smooth electrode, the photo electricaltransformation ability is greatly improved. According to MichaelGraetzel's research, the photoelectrical transformation efficiency ofthe DSSC is notably improved to 8%.

The DSSC obviously relies its efficiency on its nanoelectrode structureof titanium oxide (TiO₂). Therefore, on fabricating the TiO₂, the shape,the arrangement and the interface characteristic of nano-crystal has tobe well-controlled. The inner surface area of the TiO₂ decides how muchdye will be kept; the distribution of the holes affects the spreading ofthe redox pairs; the distribution of the granular size affects itsoptical characteristics; and the electron flow determines the connectionbetween the particles. Nowadays, a TiO₂ electrode has a electrontransferring rate of 10⁻⁴ cm²/s; so the electrons are easy to bere-combined to the dye for an reaction.

Under a best experimental environment with a best dye, Graetzel, etc.make the transformation efficiency arrive at 10% which is quite close tothat of a non-crystal system of 9%-10%; yet still worse than that of themulti-crystal system of 15%. And, as what is noteworthy, the costs foran organic dye/TiO₂ and a multi-crystal system are so high that theircosts are still uncompetitive to that of petroleum fuel, like oil orgas.

A prior art is revealed in Taiwan, called “A solar cell unit and amodule thereof”, comprising an optoelectronic transformation layer withan upper and an lower surface; an anode layer obtained on the uppersurface, comprising an anode conductive part extending out of the brimof the optoelectronic transformation layer; a cathode obtained on thelower surface, comprising a cathode conductive part extending out of thebrim of the optoelectronic transformation layer; and more than oneseparating part set at the brim of the optoelectronic transformationlayer, where the anode conductive part and the cathode conductive partis further extended out of the separating part; the optoelectronictransformation layer comprises a dye photosensitive layer and anelectrolyte; the dye photosensitive layer is deposed on the a nodelayer; and the electrolyte is filled fully between the anode layer andthe cathode layer.

Although the above DSSC has a great improvement in transformationability, the cost is high and the fabricating procedure is complex thatsome elements in the environment has to be controlled, such as thegranular size of the TiO₂ and the distribution of the particles.Besides, after the prior art of “A solar cell unit and a module thereof”is shone under the sun for a long time, the material may have aqualitative change to lose its photosensitivity with lifetime shortened.Hence, the prior arts do not fulfill users' requests on actual use.

SUMMARY OF THE INVENTION

The main purpose of the present invention is to fabricating aphotosensitized electrode with low cost and with long lifetime to beapplied in a solar cell device having enhanced absorbing ability.

To achieve the above purpose, the present invention is an InN TiO₂photosensitized electrode, comprising a substrate, a TiO₂ film and anInN photosensitive layer, where a fabrication method for thephotosensitized electrode comprises placing a substrate, coated with aTiO₂ film, in a reaction chamber; introducing hydrazoic acid (HN₃) and acompound containing indium into the reaction chamber; illuminating theresulting InP photosensitive layer with an ultraviolet light; andobtaining an InN photosensitive layer on the TiO₂ film. Accordingly, anovel InN/TiO₂ photosensitized electrode is obtained.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be better understood from the followingdetailed description of the preferred embodiment according to thepresent invention, taken in conjunction with the accompanying drawings,in which

FIG. 1 is a structural view showing a preferred embodiment according tothe present invention;

FIG. 2 is a flow view showing the fabricating of the photosensitizedelectrode;

FIG. 2A, FIG. 2B, FIG. 2C and FIG. 2D are views showing step (a), step(b), step (c), and step (d) for fabricating the photosensitizedelectrode, respectively; and

FIG. 3 is a view showing a state of use of the electrode.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The following description of the preferred embodiment is provided tounderstand the features and the structures of the present invention.

Please refer to FIG. 1, which is a structural view showing a preferredembodiment according to the present invention. As shown in the figure,the present invention is an InN(indium nitride)/TiO₂ (titanium oxide)photosensitized electrode 1, comprising a substrate 11, a TiO₂ film 12and an InN photosensitive layer 13.

The substrate 11 is an indium tin oxide (ITO) glass, an fluorine tinoxide (FTO) glass or other transparent conductive substrate.

The TiO₂ film 12 is covered on the substrate 11. The TiO₂ film 12 has ananoparticle structure, where a plurality of nanoparticles are evenlydistributed in the TiO₂ film 12, and where each nanoparticle has adiameter between 7 nm (nanometer) and 50 nm. The TiO₂ film 12 has athickness between 100 nm and 100000 nm and is made of a metal oxidehaving a high band-gap.

The InN photosensitive layer 13 is made through a chemical vapordeposition (CVD), a physical vapor deposition (PVD) or other epitaxialfilm growth method. The InN photosensitive layer 13 is coated on theTiO₂ film 12. The InN photosensitive layer 132 has a thickness between 1nm and 10000 nm. Thus, with the above structure, a novel photosensitizedelectrode is obtained.

When a light penetrates through the substrate 11 of the photosensitizedelectrode 1 into the photosensitive layer 13, an electron is injectedinto the TiO₂ film 12 from the InN photosensitive layer 13 and then theelectron is conducted to an outside circuit from the substrate, wherethe InN photosensitive layer 13 absorbs an optical wavelength between390 nm and 800 nm.

Please refer to FIG. 2 and FIG. 2A until FIG. 2D, which are a flow viewshowing the fabricating of the photosensitized electrode and viewsshowing step (a) until step (d) of the fabricating of thephotosensitized electrode. As shown in the figures, the fabricating ofthe photosensitized electrode according to the present inventioncomprises the following steps:

Step (a): A substrate 11 coated with a TiO₂ film 12 is placed into areaction chamber 2, where the TiO₂ film 12 is coated on the substrate 11through a CVD or a PCD.

Step (b): A hydrazoic acid (HN3) 31 and a compound containing indium 32is introduced into the reaction chamber 2, where the ratio of HN3 31 tothe compound containing indium 32 is between 1 and 10. The compoundcontaining indium 32 is a trimethylindium, a triethylindium, aindium-containing metallo-organic precursor or a combination ofindium-containing metallo-organic precursors. The present invention usesthe HN3 31 and the compound containing indium 32 as precursors; and theHN3 31 can be replaced with a compound containing nitrogen.

Step (c) The substrate 11 is then illuminated with an ultraviolet (UV)light, where the UV light is obtained from a continuous UV lamp, anexcimer laser, a semiconductor laser, a gas laser, a solid-state laser,a liquid laser, a chemical laser or a free-electron laser, and where theTiO2 film 12 bears a temperature between 600° C. (Celsius degree) and900° C.

Step (d): An InN photosensitive layer 13 is obtained on the TiO₂ film12. Thus, an InN photosensitized electrode 13 is obtained through theabove steps, where the total process time is between 1 hr and 8 hr.

Please refer to FIG. 3, which is a view showing a state of use of theelectrode. As shown in the figure, the photosensitized electrode 1according to the present invention is assembled with a platinum counterelectrode 51 to form a solar cell device filled with an electrolyte 52inside. The present invention can be applied to a solar cell device, aphotovoltaic device, a hydrogen generation devices and an optoelectronicdevice.

To sum up, the present invention is an InN/TiO2 photosensitizedelectrode, where a lifetime issue of the dye for a Dye-Sensitized SolarCell (DSSC) is solved; an optical absorption efficiency is enhanced; aproduction procedure is simplified; and a production cost is reduced.

The preferred embodiment herein disclosed is not intended tounnecessarily limit the scope of the invention. Therefore, simplemodifications or variations belonging to the equivalent of the scope ofthe claims and the instructions disclosed herein for a patent are allwithin the scope of the present invention.

1. An InN (indium nitride)/TiO₂ (titanium oxide) photosensitizedelectrode, comprising: a substrate; a TiO₂ film, said TiO₂ film coveringon said substrate; and an InN photosensitive layer, said InNphotosensitive layer coating on said TiO₂ film.
 2. The photosensitizedelectrode according to claim 1, wherein said substrate is a transparentconductive substrate selected from a group consisting of an indium tinoxide (ITO) glass and an fluorine tin oxide (FTO) glass.
 3. Thephotosensitized electrode according to claim 1, wherein said TiO₂ filmhas a nanoparticle structure.
 4. The photosensitized electrode accordingto claim 3, wherein said nanoparticle has a diameter between 7 nm(nanometer) and 50 nm.
 5. The photosensitized electrode according toclaim 1, wherein said TiO₂ film has a thickness between 100 nm and100000 nm.
 6. The photosensitized electrode according to claim 1,wherein said InN photosensitive layer has a thickness between 1 nm and10000 nm.
 7. The photosensitized electrode according to claim 1, whereinsaid InN photosensitive layer absorbs light having a wavelength between390 nm and 600 nm.
 8. The photosensitized electrode according to claim1, said photosensitized electrode having a fabrication method comprisingsteps of: a. placing a substrate in a reaction chamber, said substratecoated with a TiO₂ film; b. introducing a hydrazoic acid (HN₃) and acompound containing indium into said reaction chamber; c. illuminatingsaid TiO₂ film with an ultraviolet (UV) light; and d. obtaining an InNphotosensitive layer coated on said TiO₂ film.
 9. The method accordingto claim 8, wherein said compound containing indium is selected from agroup consisting of a trimethylindium, a triethylindium, aindium-containing metallo-organic precursor and a combination ofindium-containing metallo-organic precursors.
 10. The method accordingto claim 9, wherein said hydrazoic acid is a compound containingnitrogen.
 11. The method according to claim 8, wherein a ratio of saidHN₃ to said compound containing indium is between 1 and
 10. 12. Themethod according to claim 8, wherein said TiO₂ film bears a temperaturebetween 600° C. (Celsius degrees) and 900° C.
 13. The method accordingto claim 8, wherein a period of time for processing all steps of saidstep (a) until step (d) is between 1 hr (hour) and 8 hr.
 14. The methodaccording to claim 8, wherein said UV light is obtained from a lightsource selected from a group consisting of a continuous UV lamp, anexcimer laser, a semiconductor laser, a gas laser, a solid-state laser,a liquid laser, a chemical laser and a free-electron laser.